\begin{pspicture}(0,-.5)(13,7)
  \input{fig/1d-helpers.tex}
	% Box around 2x2 cell.
	\psframe*[linecolor=lightgray,fillcolor=lightgray]
					(4.6,2.6)(8.4,6.4)
	% Required Yee cells.
	\multiput(0,0)(2,0){6}{
		\Eright11
		\psframe[linestyle=dashed](.6,.6)(2.4,2.4)
	}
	% Rest of dots and arrows.
	\multiput(3,1)(2,0){5}{\Eleft00}
	\multiput(2,1)(2,0){5}{\Hright01\Eup10\Hleft21}
	\multiput(3,2)(2,0){4}{\Eright01\Hup10\Eleft21}
	\multiput(4,3)(2,0){3}{\Hright01\Eup10\Hleft21}
	\multiput(5,4)(2,0){2}{\Eright01\Hup10\Eleft21}
	% Axes.
	\Taxis016\Xaxis{1}{12}{0}  
\end{pspicture}
